One of the major problems presently confronting mass spectrometry is the analysis of low volatility compounds. This problem is especially acute in applications of mass spectrometry to studies of biological importance. We have recently developed a trapped ion cyclotron resonance mass spectrometer which is ideally suited for structural analysis of ultra-low vapor pressure compounds. Calculations indicate that sample vapor pressures as low as 10 to the 10th power Torr can be detected by this method, whereas a minimum sample vapor pressure of 10 to the minus 6th power is required for analysis with a conventional mass spectrometer and heated sample inlet probe. The most novel feature of the trapped ion cyclotron resonance mass spectrometer is its remarkable ability to trap gaseous ions. At a pressure of 4.7 x 10 to the minus 7th power Torr, 80 percent trapping efficiency is observed after 3 seconds. This feature permits chemical ionization studies at low pressures using a wide variety of positive or negative reagent ions. Structural analysis of complex, high molecular weight molecules can be performed using the powerful kinetic and equilibrium capabilities of the trapped ion cyclotron resonance technique. Initial studies will be directed toward the analysis of compounds related to nucleic acids. Applicability of the trapped ion cyclotron resonance technique will be explored for determining the structure of rare DNA bases, the structure of a cofactor for a photoreactivating enzyme isolated from mammalian leukocytes, and for sequencing oligonucleotides.